Vehicle headlamp

ABSTRACT

A vehicle headlamp including a lighting circuit unit for lighting a discharge bulb, the lighting circuit unit being provided on an exterior surface of the side wall of the lamb body that is located on the inner side of the lamp body with respect to the width direction of a vehicle. An electric supply cord extending from the lighting circuit unit is disposed along the reflecting surface backside portion of a reflector that is installed in the lamp body.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a vehicle headlamp that has adischarge bulb and more particularly to an attachment structure of alighting circuit unit to a lamp body of a vehicle headlamp.

[0003] 2. Related Art

[0004] Discharge bulbs are capable of high luminosity irradiation, andsuch bulbs have been recently adopted as a light source for a vehicleheadlamp. In such a vehicle headlamp, a lighting circuit unit forapplying high voltage to the discharge bulb for lighting it is needed.

[0005] For a vehicle headlamp that was known when discharge bulbs beganto be adopted, the lighting circuit unit was attached to a rear wall ofthe lamp body. However, as seen from FIG. 4, in the structure generallytaken, a lighting circuit unit 130 is attached to the bottom wall 112 cof a lamp body 112 where it is easy to secure an attachment space forthe lighting circuit unit 130.

[0006] However, this conventional vehicle headlamp has problems. Whenthe lighting circuit unit 130 is attached to the bottom wall 112 c, mostof the heat generated in the lighting circuit unit 130 following thelighting of the discharge bulb 118 is diffused upward. This promotes atemperature rise in a lamp chamber 140 heated by the lighted dischargebulb 118.

[0007] Moreover, a typical reflector 116 as shown in FIG. 4 has a lowerend thereof formed with a bottom wall 116 c. When the lighting circuitunit 130 is attached to the bottom wall 112 c of the lamp body 112, itis necessary to secure a clearance between the bottom wall 112 c and thebottom wall 116 c of the reflector 116 for installing wires for a bulbsocket 124 and an electric supply cord 126 that connects the lightingcircuit unit 130 to the discharge bulb 118. As a result, a sizereduction in the reflector 116 is inevitable to some extent, resultingin the sacrifice of corresponding light distribution performance of thelamp.

SUMMARY OF THE INVENTION

[0008] Accordingly, it is an object of the present invention to providea vehicle headlamp in which a lighting circuit unit for the dischargebulb is attached to the lamp body so as not to cause a temperature risein the lamp chamber and not to sacrifice light distribution performanceof the lamp.

[0009] In other words, the present invention accomplishes the aboveobjects by way applying an innovation in an attachment position of thelighting circuit unit on a lamp body.

[0010] More specifically, the above object is accomplished by a uniquestructure of the present invention for a vehicle headlamp that comprisesa discharge bulb, a reflector for supporting the discharge bulb, a lampbody that houses the reflector therein, a transparent cover attached toa front end open portion of the lamp body, and a lighting circuit unitfor lighting the discharge bulb, and in the present invention thelighting circuit unit is attached to an exterior surface of a side wallof the lamp body that is located on an inner side in the vehicle widthdirection.

[0011] The specific shape and attachment posture of the “lightingcircuit unit” with respect to the lamp body is not limited as long assuch unit is attached to the exterior surface of the lamp body's sidewall that is located on the inner side in the vehicle width direction.

[0012] As seen from the above, the vehicle headlamp according to thepresent invention includes a discharge bulb, and the lighting circuitunit for lighting this discharge bulb is attached to the exteriorsurface of the lamp body's side wall that is located on the inner sideof the lamp body in the vehicle width direction. Accordingly, thefollowing operational advantages are obtained.

[0013] By way of attaching the lighting circuit unit to the side wall ofthe lamp body, heat generated in the lighting circuit unit after thelighting of the discharge bulb is diffused upward or sideward withrespect to the lighting circuit unit. Accordingly, a temperature rise inthe lamp chamber can be effectively restrained.

[0014] Further, the side wall extending from the side edge of thereflector is generally not formed so that its reflecting surface is cutlarge from the position relatively close to the rear apex portion of thereflector as in the bottom wall. Rather, the side wall of a reflector isformed so that its reflecting surface is cut small from a position at aconsiderable distance in front of the rear apex portion of thereflector. Therefore, by way of attaching the lighting circuit unit tothe lamp body' inner side wall (and not to the outer side wall) as inthe present invention, it is possible to install the electric supplycord, that extends from the lighting circuit unit, so as to be disposedalong the reflecting surface back side portion of the reflector. Theaiming mechanism for tilting the reflector is generally provided betweenthe reflecting surface back portion and the side and rear walls of thelamp body; accordingly, a relatively large clearance is secured from thebeginning. Therefore, contrary to the conventional structure in whichthe lighting circuit unit is attached to the bottom wall of the lampbody, it is not necessary in the present invention to secure a largeclearance for the electric supply between the lamp body and thereflector. Thus, the size of the reflector does not need to be reducedfor installing the electric supply cord.

[0015] Meanwhile, a transparent cover of a vehicle headlamp is generallyinclined toward outside in the vehicle width direction and backward withrespect to the vehicle headlamp. As a result, the front-end open portionof the lamp body is also inclined toward outside in the vehicle widthdirection and backward with respect to the lamp body. Therefore, as tothe side walls of the lamp body, the side wall that is located on theinner side in the vehicle width direction has a larger area compared tothe side wall that is located on the outer side in the vehicle widthdirection. In this regard, since the lighting circuit unit is attachedto the exterior surface of the side wall on the inner side in thevehicle width direction in the present invention, a relatively largeattachment space is secured.

[0016] As seen from the above, in the vehicle headlamp equipped with adischarge bulb according to the present invention, the lighting circuitunit is attached to the lamp body without causing a temperature rise inthe lamp chamber or without sacrificing light distribution performanceof the lamp.

[0017] In the above described structure of the vehicle headlamp of thepresent invention, the reflector can be designed so that a firstreflector portion thereof for supporting the discharge bulb and a secondreflector portion thereof for supporting a light source bulb other thanthe discharge bulb are disposed vertically on two levels. Accordingly, alarge height dimension can be secured for the side wall of the lampbody, and therefore, the attachment space for the lighting circuit unitis further enlarged. Furthermore, in this two level design of thereflector, it is possible to dispose the electric supply cord, thatextends from the light circuit unit, along the recessed area that isbetween the reflecting surface back side portion of the first reflectorportion and the reflecting surface back side portion of the secondreflector portion. Thus the space in the lamp chamber can be effectivelyused, thus being able to reduce the overall size of the lamp.

[0018] Moreover, in the above-described structure, the front end openportion of the lamp body is formed wrapping widely around toward outsidein the vehicle width direction and backward with respect to the lampbody. In other words, the side wall of the lamp body on the outer sidein the vehicle width direction does not virtually exist or is verynarrow. Further, the bottom wall of such a lamp body has a wedge-likeshape. Therefore, the structure of the present invention in which thelighting circuit unit is attached to the side wall on the inner side inthe vehicle width direction is particularly effective. The above phrase“wrapping widely around toward outside in the vehicle width directionand backward” specifically refers to the structure in which the end ofthe front end open portion of the lamp body on the outer side in thevehicle width direction body is positioned further to the rear than adischarge light emitting portion of the discharge bulb.

[0019] Meanwhile, when attaching the lighting circuit unit to theexterior surface of the side wall of the lamp body, it is preferable, asseen in the present invention, to attach a unit cover for covering thelighting circuit unit to the exterior surface of the side wall in orderto improve the water-proof and dust-proof functions. In this case, theunit cover is attached with screws to the side wall of the lamp body atlocations near upper and lower edge portions of the unit cover. Withthis unit cover, the strength around the attachment portion of thelighting circuit unit on the side wall of the lamp body is enhanced.

[0020] Moreover, with the above covering structure, the sealing surfaceof the unit cover and the side wall of the lamp body extend on avertical plane or on a substantially vertical plane. Therefore, whenwater enters the unit cover, the water is easily drained out of the unitcover by its own weight. Thus, in the present invention, the unit coverhas a simple waterproof structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a front view of a vehicle headlamp according to anembodiment of the present invention;

[0022]FIG. 2 is a horizontal sectional view taken along the line II-IIin FIG. 1;

[0023]FIG. 3 is a side view taken in the direction of arrow III in FIG.1; and

[0024]FIG. 4 is a side view of a conventional vehicle headlamp in crosssection.

DETAILED DESCRIPTION OF THE INVENTION

[0025] A typical embodiment of the present invention will be describedbelow with reference to the accompanying drawings.

[0026] As seen from FIGS. 1 through 3, a vehicle headlamp 10 includes areflector 16. The reflector 16 is disposed in a lamp chamber 40 that isformed by a lamp body 12 and a plain transparent cover 14 attached tothe front end open portion 12 a of the lamp body 12. The reflector 16 istiltable in the vertical and lateral directions via an aiming mechanism(not shown). An extension reflector 22 is also provided in the lampchamber 40. The reflector 22 is located in front of the reflector 16 andfollows the shape of the opening periphery of the lamp chamber 40.

[0027] The reflector 16 comprises a first reflector portion 16A and asecond reflector portion 16B that are horizontally rectangular whenviewed from the front of the lamp body 12. These reflector portions 16Aand 16B are disposed vertically on two levels so that the firstreflector portion 16A is on top of the second reflector portion 16B asbest seen from FIG. 3.

[0028] As seen from FIG. 2, a discharge bulb (metal halide bulb) 18A anda shade 20A for covering the front of the discharge bulb 18A aresupported at the rear apex portion of the first reflector portion 16A.The reflecting surface 16Aa of the first reflector portion 16A is, asseen from FIG. 1, formed with a plurality of reflective elements on aparaboloid of revolution with an optical axis Ax1 that extends in thelongitudinal direction as a central axis. The reflecting surface 16Aathus having the reflective elements radiates a beam in a distributionpattern for a low beam by reflecting the light from the discharge bulb18A forward in a diffused and deflected manner.

[0029] On the other hand, a halogen bulb (H4 bulb) 18B and a shade 20Bfor covering the front of the halogen bulb 18B are supported at the rearapex portion of the second reflector portion 16B. The reflecting surface16Ba of the second reflector portion 16B is formed with a plurality ofreflective elements on a paraboloid of revolution with an optical axisAx2 that extends in the longitudinal direction as a central axis. Thereflecting surface 16Ba thus having the reflective elements radiates abeam in a distribution pattern for a high beam or in a distributionpattern for a fog lamp by reflecting the light from the discharge bulb18B forward in a diffused and deflected manner.

[0030] The reflector 16 is formed on its peripheral portion with anupper wall 16 b, a bottom wall 16 c, and a pair of right and left sidewalls 16 d and 16 e. The upper wall 16 b and the bottom wall 16 c (seeFIG. 3) are formed so that the reflecting surfaces 16Aa and 16Ba areeach cut large from a position relatively close to the rear apex portionof the reflector 16, while the side walls 16 d and 16 e (see FIG. 2) areformed so that the reflecting surfaces 16Aa and 16Ba are cut small froma position at a considerable distance in front of the rear apex portionof the reflector 16.

[0031] As best seen from FIG. 2, the transparent cover 14 is formedwrapping widely around toward outside in the vehicle width direction andbackward with respect to the cover 14. As a result, the front end openportion 12 a of the lamp body 12 is also formed wrapping widely aroundtoward outside in the vehicle width direction and backward with respectto the front end open portion, and the end portion of this front endopen portion 12 a on the outer side (on the right side in FIG. 2) in thevehicle width direction is positioned further to the rear than thedischarge light emitting portion 18Aa of the discharge bulb 18A. Forthis reason, the lamp body 12 has a side wall 12 d that has a relativelylarge depth dimension in the longitudinal direction and is formed on theinner side (on the left side in FIG. 2) of the lamp body 12 in thevehicle width direction (the right and left direction in FIG. 2). On itsouter side (on the right side in FIG. 2), however, the lamp body 12 hasno such side wall in the vehicle width direction.

[0032] The height dimension of the side wall 12 d and the rear wall 12 bof the lamp body 12 is set to be relatively large values so the lampbody 12 houses the reflector 16 that has the first and second reflectorportions 16A and 16B disposed vertically on two levels as describedabove.

[0033] An open portion 12 i is formed on the rear wall 12 b of the lampbody 12. The open portion 12 i is for facilitating change of thedischarge bulb 18A and the halogen bulb 18B. A back cover 28 is attachedto the open portion 12 i.

[0034] As seen from FIG. 2, the discharge bulb 18A is connected to thelighting circuit unit 30 via the bulb socket 24 and the electric supplycord 26. The lighting circuit unit 30, which is provided with a startingcircuit and a stable circuit housed in a thin rectangular parallelepipedcase, is attached to the exterior surface of the side wall 12 d of thelamp body 12. This side wall 12 d is located, as described above, on theinner side of the lamp body 12 with respect to the width direction of avehicle (not shown). The lighting circuit unit 30 is set so that itslonger sides are in a vertical direction as seen from FIG. 3. Thisattachment of the lighting circuit unit 30 is performed by making a pairof upper and lower tabs 30 a (see FIG. 3) formed on the rear end face ofthe lighting circuit unit 30 abut against a pair of upper and lowerbosses 12 e formed on the side wall 12 d and by fixing them with screws42.

[0035] The electric supply cord 26 extends out from the lighting circuitunit 30. More specifically, the electric supply cord 26 extends from aportion that is near the rear end (see FIG. 2) of a substantiallycentral position in the vertical direction (see FIG. 3) on the side faceof the lighting circuit unit 30 that is located on the outer side (theright side in FIG. 2) in the vehicle width direction. Meanwhile, a cordreceiving hole 12 f is formed at a substantially center position of theside wall 12 d of the lamp body 12 in the vertical direction (see FIG.3).

[0036] Thus, when the lighting circuit unit 30 is mounted, the electricsupply cord 26 together with the bulb socket 24 is inserted in the lampchamber 40 through the cord receiving hole 12 f, and the bulb socket 24is fitted to the rear end portion of the discharge bulb 18A. In thiscase, the electric supply cord 26 is, as seen from FIG. 3, disposedalong the reflecting surface back side portion 16 f of the reflector 16in the lamp chamber 40. Since the cord receiving hole 12 f is formed ata substantially center position in the vertical direction of the sidewall 12 d of the lamp body 12, it is possible to dispose the electricsupply cord 26 along the recessed area formed between the reflectingsurface back side portion 16Af of the first reflector portion 16A andthe reflecting surface back side portion 16Bf of the second reflectorportion 16B of the reflector 16.

[0037] A vertically elongated rectangular unit cover 32 is attached tothe exterior surface of the side wall 12 d of the lamp body 12, thuscovering the lighting circuit unit 30. This attachment of the unit cover32 to the lamp body 12 is performed: by inserting a seal leg portion 32a that is formed over the entire peripheral portion of the unit cover 32into a seal groove 12 g that is formed so as to project on the exteriorsurface of the side wall 12 d with a gasket 34 in between, by making twopairs of tabs 32 b that are formed on both upper and lower edge portionsof the unit cover 32 abut against two pairs of upper and lower bossesformed near the upper and lower edge portions of the side wall 12 d, andthen by fixing the tabs 32 b with screws 44. The unit cover 32 acts towater-proof and dust-proof the cord receiving hole 12 f.

[0038] In addition, a hole for drainage (not shown) is formed near asealing surface of the seal leg portion 32 a of the unit cover 32 andthe seal groove 12 g of the side wall 12 d at the lower end of the unitcover 32.

[0039] As described above in detail, the vehicle headlamp 10 of theshown embodiment contains the discharge bulb 18A, and the lightingcircuit unit 30 for lighting this discharge bulb 18A is attached to theexterior surface of the side wall 12 d of the lamp body 12 that islocated on the inner side in the vehicle width direction. Accordingly,the operational advantages as described below are obtained.

[0040] Since the lighting circuit unit 30 is attached to the side wall12 d of the lamp body 12, heat generated in the lighting circuit unit 30after lighting the discharge bulb 18A is diffused upward or sideward ofthe lighting circuit unit 30. Accordingly, a temperature rise in thelamp chamber 40 is effectively prevented.

[0041] Moreover, the side wall 16 d formed on the side edge portion ofthe reflector 16 on the inner side in the vehicle width direction isformed so that the reflecting surfaces 16Aa and 16Ba are cut small fromthe position at a considerable distance in front of the rear apexportion of the reflector 16. Accordingly, the electric supply cord 26,that extends from the lighting circuit unit 30, can be disposed alongthe reflecting surface back side portion 16 f of the reflector 16. Theaiming mechanism for tilting the reflector 16 is provided between thereflecting surface back side portion 16 f and the side wall 12 d and therear wall 12 b of the lamp body 12, and this structure means that thelamp body 12 has a relatively large clearance. Therefore, unlike theconventional headlamps in which the lighting circuit unit is attached tothe bottom wall of the lamp body 12, the necessity of securing a largeclearance between the lamp body 12 and the reflector 16 for disposingthe electric supply cord 26 is eliminated in the present invention. Itis thus not necessary to reduce the size of the reflector 16 in view ofthe electric supply cord 26.

[0042] Furthermore, in the vehicle headlamp 10 of the shown embodiment,the transparent cover 14 and the front end open portion 12 a of the lampbody 12 are formed wrapping widely around toward outside in the vehiclewidth direction and their backward directions. Accordingly, on one sideof the lamp body that is located on the outer side in the vehicle widthdirection, there is no such flat side wall as side wall 12 d. Thus, theside wall 12 d on another side or on the inner side in the vehicle widthdirection can serve as an attachment surface for the lighting circuitunit 30, and a relatively large attachment space is secured. Thisadvantage is not hindered even if the bottom wall 12 c of the lamp body12 has a wedge-like shape.

[0043] Thus, in the above embodiment, the lighting circuit unit 30 isattached to the lamp body 12 without causing a temperature rise in thelamp chamber 40 or sacrificing light distribution performance of thelamp.

[0044] Furthermore, since the reflector 16 has a structure in which thefirst reflector portion 16A for supporting the discharge bulb 18A andthe second reflector portion 16B for supporting the halogen bulb 18B aredisposed vertically on two levels, a large height dimension of the sidewall 12 d of the lamp body 12 is obtained; and as a result, a largerattachment space for the lighting circuit unit 30 can be obtained.Accordingly, the lighting circuit unit 30 can be disposed within an areadefined by the side wall 12 d on the exterior surface of the side wall12 d of the lamp body 12, and it is possible to effectively avoidinterference with vehicle components that are provided near the lampbody.

[0045] In addition, the electric supply cord 26 that extends out fromthe lighting circuit unit 30 is disposed so as to be along the recessedarea formed between the reflecting surface back side portion 16Af of thefirst reflector portion 16A and the reflecting surface back side portion16Bf of the second reflector portion 16B. Thus, an effective use ofspace in the lamp chamber 40 is assured, and the overall size of thelamp can be reduced.

[0046] Moreover, in the shown embodiment, the unit cover 32 for coveringthe lighting circuit unit 30 that is in a longitudinally elongated shapeis attached to the exterior surface of the side wall 12 d of the lampbody 12, and the unit cover 32 is fixed to both upper and lower edgeportions of the side wall 12 d with screws. Accordingly, the strengtharound the attachment portion of the lighting circuit unit 30 in theside wall 12 d is enhanced. Moreover, since the seal groove 12 g isformed on the exterior surface of the side wall 12 d so as to surroundthe lighting circuit unit 30, the rigidity of the side wall 12 d canalso be enhanced.

[0047] Moreover, the sealing surface of the unit cover 32 and the sidewall 12 d of the lamp body 12 extend on a substantially vertical plane.Therefore, even if water enters the unit cover 32, the water can beeasily drained out of the unit cover 32 by its own weight, thus awaterproof structure can be easily obtained for the unit cover.

1. A vehicle headlamp comprising: a discharge bulb, a reflector forsupporting said discharge bulb, a lamp body for housing said reflector,a transparent cover attached to a front end open portion of said lampbody, and a lighting circuit unit for lighting said discharge bulb,wherein said lighting circuit unit is provided on an exterior surface ofa side wall of said lamp body, said side wall being located on an innerside of said lamp body in a vehicle width direction.
 2. The vehicleheadlamp according to claim 1, wherein said reflector comprises a firstreflector portion for supporting said discharge bulb, and a secondreflector portion for supporting a light source bulb other than saiddischarge bulb, wherein said first and second reflector portions aredisposed vertically.
 3. The vehicle headlamp according to claim 1,wherein said front end open portion of said lamp body is formed so as tobe wrapping widely around toward an outside in said vehicle widthdirection and backward with respect to said front end open portion. 4.The vehicle headlamp according to claim 1, further comprising a unitcover for covering said lighting circuit unit, said unit cover beingmounted on said exterior surface of said side wall on said inner side insaid vehicle width direction so that said unit cover is attached by wayof fixing said unit cover with screws to said side wall at portions nearboth upper and lower edges of said side wall.
 5. The vehicle headlampaccording to claim 2, wherein said front end open portion of said lampbody is formed so as to be wrapping widely around toward an outside insaid vehicle width direction and backward with respect to said front endopen portion.
 6. The vehicle headlamp according to claim 2, furthercomprising a unit cover for covering said lighting circuit unit, saidunit cover being mounted on said exterior surface of said side wall onsaid inner side in said vehicle width direction so that said unit coveris attached by way of fixing said unit cover with screws to said sidewall at portions near both upper and lower edges of said side wall. 7.The vehicle headlamp according to claim 3, further comprising a unitcover for covering said lighting circuit unit, said unit cover beingmounted on said exterior surface of said side wall on said inner side insaid vehicle width direction so that said unit cover is attached by wayof fixing said unit cover with screws to said side wall at portions nearboth upper and lower edges of said side wall.
 8. The vehicle headlampaccording to claim 5, further comprising a unit cover for covering saidlighting circuit unit, said unit cover being mounted on said exteriorsurface of said side wall on said inner side in said vehicle widthdirection so that said unit cover is attached by way of fixing said unitcover with screws to said side wall at portions near both upper andlower edges of said side wall.